1. Field of the Invention
The present invention relates to a video conferencing system, and more particularly, to a multi-point video conferencing system which improves the method for placing plural images transmitted from plural users separated geographically on the display of each terminal.
2. Description of the Related Art
FIG. 1 is a schematic diagram of a conventional multi-point video conferencing system. The system of FIG. 1 is disclosed in U.S. Pat. No. 5,446,491 issued Aug. 29, 1995 to Shinbata et al. and entitled "Multi-point Video Conference System" wherein each terminal comprises a shared frame memory to store information from other terminals.
The video conferencing system shown in FIG. 1 includes a plurality of terminals for motion picture conferencing 10a through 10d, and a communications network 12 for transmitting and switching encoded motion picture data from the terminals 10a through 10d. Here, each of the terminals 10a through 10d have the same configuration.
FIG. 2 is a detailed block diagram of one of the terminals 10a through 10d shown in FIG. 1. Each terminal includes a video camera 102, an encoder 104, a multi-point decoder 106, and a display 108.
The encoder 104 encodes and packetizes the motion picture signals output by the video camera 102 in units of blocks. The multi-point decoder 106 restores the packets received from the other terminals through the communications network 12 into the original motion pictures. The display 108 displays the data transmitted from the multi-point decoder 106.
In particular, the multi-point decoder 106 includes an image processor, a channel selection controller, a shared frame memory and a display memory. The image processor processes an input image in a time divisional multiplexing scheme. The channel selection controller determines the transmission point of received packets according to the information of the received packets and notifies the image processor of the transmission point. The shared frame memory stores information of a plurality of images transmitted from the plurality of terminals. The display memory synchronously outputs video information stored in the shared frame memory.
The conventional multi-point video conferencing system having the aforementioned configuration is constructed to operate the multi-point video decoder in a time divisional multiplexing scheme to display information of a plurality of compressed images received from different terminals on a display device. In such a configuration, as the number of terminals involved in the video conference system increases, the amount of data to be calculated in a processor incorporated in the multi-point video decoder increases accordingly. Thus, to complete decoding within a limited time, the calculating capacity of the processor must be enhanced, which increases costs of the system.